BREWER – Though DHL denies union activity played a role in its decision to hire a Pennsylvania firm to run its local operations, a supervisor with the subcontractor allegedly told prospective employees this was the case, according to a complaint issued last week by federal labor regulators.

The supervisor, Dwayne Gilbert, allegedly told former Black Bear Courier employees that their decision to unionize was the reason their company lost its DHL contract and why his employer, Rydbom Express of Harrisburg, Pa., was hired instead, the complaint indicates. The complaint was issued June 22 by the National Labor Relations Board.

Black Bear Courier had delivered packages for DHL in the Bangor and Presque Isle areas for more than 10 years when, in January, its employees voted to join the International Brotherhood of Teamsters. Two months later, Black Bear no longer had a contract with the global shipping giant and laid off its 48 drivers.

Richard Gibbs of DHL’s corporate U.S. headquarters in Plantation, Fla., said Tuesday in a message that rather than losing its contract with DHL, Black Bear Courier failed to renew its contract with DHL. He said DHL is not involved in the dispute, which is “strictly an issue between Rydbom Express and the Teamsters.”

A dozen former Black Bear Courier employees who initially were not hired by Rydbom returned to their delivery jobs Tuesday after picketing DHL’s leased offices on Parkway South for months. The 12 drivers had expected to return Monday to their jobs, but were delayed after Rydbom tried to make them take drug tests even though it does not have a drug-testing policy that has been approved by the state, David White of the Teamsters’ national office said Tuesday.

Attempts Tuesday to contact Doug Rydbom, owner of Rydbom Express, were unsuccessful.

According to Adam Fisher of the Maine Department of Labor, employers in Maine are allowed to test their employees for drugs but are required to have a drug-testing policy that has been approved by the state, unless they are exempted by federal law. Fisher said Tuesday that the Labor Department cannot comment about specific alleged violations of state drug-testing laws but that it does investigate such claims.

Though the drivers have returned to work, union officials predict it may take months before the matter is fully resolved and the drivers have an employment contract with Rydbom. James Carson, president of Teamsters Local 340 in South Portland, said Monday that Rydbom owes the 12 drivers a total of $70,000 in back pay. Carson also said he doubted that Rydbom has enough work to keep the 22 nonunion workers it hired in Brewer before the union drivers were able to get their jobs back.

Teamsters officials have filed a charge with the labor relations board accusing Rydbom of violating federal labor laws. In the charge, the union claims Gilbert violated the National Labor Relations Act in March when he allegedly interrogated and threatened prospective employees about their union activity and created an atmosphere of surveillance.

Despite DHL’s claims that it has nothing to do with the labor dispute, Teamsters officials have said DHL ultimately is responsible for the situation in Brewer and that the shipping company is involved in similar disputes in other parts of the country.

A hearing on the complaint is expected to be held before a judge on Aug. 2, according to Kathleen McCarthy of the NLRB’s Boston office. Where the hearing will take place has not been determined, but it will be “somewhere in the Bangor area,” McCarthy has said.

DHL was founded in 1969 in San Francisco but now is owned by Deutsche Post World Net, the former state-owned postal service in Germany. DHL has more than 170,000 full-time employees worldwide and in 2004 earned more than $32 billion in revenue, according to information provided by the company.